Sexual precocity is defined as the appearance of any sign of secondary sexual maturation at an age more than two standard deviations below the mean (age 8 for girls). In cases of sexual precocity, production of endogenous estrogen at an early age results in the premature onset of puberty. Several different forms of sexual precocity, also termed precocious puberty, have been identified including true precocious puberty (complete isosexual precocity), incomplete isosexual precocity, and contrasexual precocity. Variations include premature thelarche, premature isolated menarche, and premature adrenarche.
Complete isosexual precocity results from early activation of hypothalamic LHRH pulse generator pituitary gonadotropin-gonadal axis and is thus LHRH dependent. This form of precocious puberty is more prevalent in girls than boys and results in the appearance of breast development, enlargement of the laboria minora, and maturational changes in the vaginal mucosa along with pubic hair appearance. Accordingly, sexual maturation is more rapid than in normal puberty. The rapid growth is associated with increases in serum IGFI levels because of increased gonadal estrogen secretion. True precocious puberty often results from CNS tumors (including optic and hypothalamic gliomas, astrocytomas, and ependymonas) which interfere with the LHRH pulse generator in childhood. Other CNS diseases often association with this form of early puberty include hydrocephalus, encephalitis, static cerebral encephalopathy and brain abcess.
Currently, three principal agents have been used to treat true precocious puberty including medroxyprogesterone acetate, cyproterone acetate, and LHRH agonists. The former two agents reverse or stop secondary sexual characteristics but do not effect final height, particularly for girls. The lack of effect on final height is presumably due to the action of circulating estradiol on skeletal growth. Thus, these agents do not correct for the excessive amount of circulating estradiol. LHRH agonists are currently the therapy of choice for true precocious puberty and act to block the effects endogenous LHRH and functions as selective, highly specific inhibitors of estrogen secretion without interfering directly with the release of other pituitary hormones. Discontinuing treatment results in reversal of estrogen suppression and allows for progression of sexual maturation. Side effects include local systematic allergic reactions.
Incomplete isosexual precocity results from premature estrogen production independent of endogenous LHRH secretion. In girls, this disorder results from autonomous secretion of estrogen by ovarian cysts or tumors, an adrenal neoplasm, or inadvertent exposure to estrogen. Ovarian masses which produce estrogen include autonomous ovarian follicular cysts, granulosa cell tumor of the ovary, as well as others. Other variations of this disorder include McCune-Albright Syndrome and juvenile hypothyroidism.